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A nasty little iTunes/iOS bug may be causing media sync issues

November 18th update: My sync issues returned, but due to a different cause this time. Details in this post.

After complaining to Tim Cook, and separately starting a (now closed) support ticket, it appears that my iOS/iTunes sync nightmare has finally come to an end!

I have not seen a progress bar that busy since the day I brought my iPhone 6 back home. Whatever I tried, iTunes simply would not sync everything in my library. In the end, the problem turned out to be as simple—but as deadly—as this:

In the current version of iTunes/iOS, there’s a bug that only appears when you have duplicates of purchased songs. When encountered, a duplicate of a purchased song will (almost always) cause iTunes to silently stop syncing.

This is a known-to-Apple issue, and it will be fixed in a forthcoming update. I’m fairly certain it’s an iTunes bug, but as Apple didn’t clearly state which it was, I’m calling it iTunes/iOS. Either way, until it’s fixed, it’s a really bad bug.

Here’s what happens: If you have duplicates of purchased songs, iTunes simply silently stops syncing when it hits one of those duplicates. From your perspective, it will look like everything is working—iTunes never throws an error, and it proceeds through all six (or seven or whatever) steps of the sync process, as seen in the status window of iTunes.

But behind the scenes, nothing is happening—at least, nothing relative to syncing your files. As seen by my troubles, this can be incredibly frustrating and hard to fix.

Continue reading to see how I was able to finally (with Apple’s help) get my devices syncing again—the tricky part is finding all the duplicates, because they’re not all obvious. Also note that if you are not having sync issues, I wouldn’t worry about duplicates—no need to endanger what’s already working well!

The “tell”

If you’re affected by this bug, you’ll find that your iOS device will get some, but not all, of your content. When you look at the device in iTunes, you’ll see something like this:

Those items with the gray dotted circle didn’t actually sync—iTunes told the iOS device the files were coming (so they show up in the list), but the file itself didn’t transfer. What seems to happen is that iTunes will sync up until it hits a duplicate of a purchased song, then it just stops (without telling you it stopped).

The fix

To fix the problem, you have to get rid of the duplicates—note that it’s only duplicates of purchased songs that cause the problem. In theory, this should be as simple as selecting your Music library, then using View > Show Duplicates. I did that first, and went through the list of matches to find actual duplicates of purchased songs.

I found a few, and removed them, but sync still wouldn’t work. Eventually, iTunes wasn’t reporting any duplicates, so I was somewhat stuck. I’d then send my sync log files back to Apple (they had me install a logging profile), and they’d be able to identify the next song that caused the problem. I’d remove that one, and then we’d then repeat this process, one painfully slow song file at a time. Ugh.

Why didn’t iTunes see these duplicates? Because they’re just different enough to not meet iTunes’ criteria, it seems. For example, here’s a duplicate that Apple identified which passed iTunes’ filters:

As you can see, the artist and time are identical, but the title and album are not. Listening to each track, though, they sounded identical to my ear. When you look at the Get Info window for these songs, you can see some other differences (click to zoom, wide window required!):

Notice that the file sizes are slightly different, and that one item has a purchase date while the other does not. These differences are enough that iTunes doesn’t think these files are duplicates, but are close enough to trigger the nasty bug.

The tool

So how do you find these devious semi-duplicates, if iTunes won’t identify them? I turned to Dupin ($15), Doug Adams’ excellent duplicate finder. I tried various combinations of Criteria settings to make sure I was getting all the dupes; this one was particularly effective:

By searching on identical album, artist and track numbers, I could find all those duplicates that had different song titles (the first three songs above, for instance, all have illegitimate dupes). Not everything found would be a true “bad” duplicate, as some CDs are just weird. You can even see that in the screenshot—Counting Crows’ Holiday in Spain and Paved Paradise are both track number 13 on Hard Candy.

Instead of using Dupin to remove the dupes (which it can do), I just switched back to iTunes and decided which one to keep and which one to delete.

After I completed this process—I found about 20 such files, all much older purchases—I was able to sync my iPhone and get 100% of my content transferred—hooray!

A very important heads up

When you first connect your iOS device after clearing your duplicates, you may see this dialog:

If you see this dialog, it’s really important that you click the Don’t Transfer button! If you do transfer the purchases back, you’ll be recreating your duplicates. And that would not be a good thing to do. (Ideally, you’ll have transferred any other legit purchases prior to clearing out duplicates, otherwise you’ll need to redownload them.)

So how’d it happen?

Just where did the duplicates come from? That’s a great question, and one I can’t completely answer. Every duplicate I found was a very old iTunes purchase—most from 2003, none newer than 2009. I don’t use iTunes Match, so it couldn’t have been some automatic thing that just happened. And all the duplicates have notable changes—some have a higher bit rate, some are DRM free vs. protected, some are longer in duration, etc.

It appears to me that, somehow at some point in time, I must have told iTunes to upgrade my collection (perhaps related to the removal of DRM, many years ago?). Those new versions should have replaced the old versions, but for whatever reason, they did not.

Years pass, and there’s no problem, because this bug is apparently a recent arrival. But once the “bugged” version of iTunes was on my Mac, the duplicate songs became sync killers.

Wrapping it all up

This was a long painful process—it’s only been four days since I picked up my iPhone, but solving the sync issue is about all I’ve been doing since then. I thank Apple for the prompt response to my issue, and for working with me to get everything working again. Everyone was incredibly professional and seemed genuinely interested in solving the problem—even on a Sunday morning.

Apple’s “normal” tech support folks were also very good, even if they didn’t seem to have the knowledge to solve the problem. They spent quite a bit of time with me, making sure they understood the problem. They checked in with me yesterday, to let me know they were still working on it.

Regardless of who solved it, I’m just very happy it’s solved…and hopefully this article will help someone else out of the same situation.


Add a Comment
  1. this is nothing to do with duplicates, I have the same issue and have checked that the files only exist uniquely

    1. Bob:

      I didn’t say this was the *only* cause of such issues. I said it *may* be a cause of such issues. There are many things that can muck with iTunes sync — I’ve found (and still find, in fact) that iPhoto photos can cause it to hang up. But there is no doubt that these duplicates can cause sync issues; that was confirmed directly by Apple.


      1. From the yellow box at the top of the article

        “In the current version of iTunes/iOS, there’s a bug that ONLY appears when you have duplicates of purchased songs. When encountered, a duplicate of a purchased song will (almost always) cause iTunes to silently stop syncing.” (my emphasis on the only in uppercase).

        It seems to me like you said it’s the only cause of such a bug appearing. I too have exactly the same symptoms as the bug you describe but for an entire album I just purchased directly from itunes. I am certain there are definitely no duplicates. At least not that I can in any way detect through normal means.


  2. Thank you for the post. I have been wrestling with this sync issue for close to a week now on IOs 9 beta. I tried everything I could think of, 4 service calls with Applecare, even got escalated but they had no clue how to even start to tackle this. The hubris calling themselves “genius”; from simple reboot, to “have you updated itunes?”, to blaming Windows, and then asking me to restore my iphone 3 times… “sure why not. Try 1 and 2 didn’t work maybe another try will…” Nothing they asked me to try made sense. But yours did. I tried deleting all my duplicate purchased items and everything sync’d without issues

  3. i was on the phone with apple for 3 hours trying to fix this and once I did it myself I was fine. Reset your phone and when it gives you the option to restore from icloud or start as a new phone start as a new phone. plug it into your computer and sync al the music. Once youre sure all of it is there, then go to setting and to icloud, type in your password and set it up from there. Youll have to re download all of your apps and stuff but if you love/need your music as much as I do its worth it

  4. Just came here to say that I had this problem, and your solution fixed it. In my case I had two copies of “Johnny Cash & U2 – The Wanderer”, one bought through iTunes and one *cough* acquired by other means. Once I removed the file – and I don’t know which of the two copies it was – from the playlist I was trying to sync to my iphone, it “unclogged” the sync process and the remaining tracks went across. Thank you!
    FWIW: iPhone 5, iOS 7.1.2, iTunes on OSX 10.9.5, syncing over wifi.

  5. This was incredibly helpful for me – thanks for writing and posting. Amazing that Apple still hasn’t fixed this issue…

  6. I solved this on my computer.

    The database was corrupted. Which happened when I had found songs at a location and the information wasn’t being written to the id3 tag but was apart of the database. Meaning the song copied to the phone was different than that of what the database had.

    To fix this I deleted the songs from my itunes library and re imported them manually. d

    Then restarted the phone and synced. Ran another sync and problem was gone.

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